Initiating in situ combustion using an autoignitible composition



United States Patent O US. Cl. 166-260 8 Claims ABSTRACT OF THEDISCLOSURE A mixture of tung oil and tall oil fatty acid is used forinitiating in situ combustion in oil stratum containing water and havinga low initial temperature.

This invention relates to a process for initiating in situ combustion inoil stratum. In one aspect this invention relates to a process forinitiating in situ combustion in oil stratum containing water at lowinitial temperatures. In another aspect this invention relates to aprocess wherein a mixture of tung oil and tall oil fatty acid is usedfor initiating in situ combustion in oil stratum containing water andhaving a low initial temperature.

There has been much work done in the past few years involving in situcombustion in oil stratum to increase the oil and oil products producedfrom the stratum. One area of work has been with autoignitible fluids.General y the autoignitible fluid is injected into the oil stratum andthen the autoignitible fluid in the stratum is contacted with air orother oxgen-containing, combustion supporting gases. When the air orother oxygen-containing, combustion supporting gas comes in contact withthe autoignitible fluid, the temperature in the formation is in creasedto at least the combustion temperature of the car bonaceous material(such as oil, oil residue, tar, etc.) in the stratum. This incerase intemperature is due to the oxidation reaction of the autoignitible fluidwhen it contacts the air or other oxygen-containing, combustionsupporting gas. The use of tung oil, linseed oil or other knownautoignition fluids has worked well for oil wells where the initialtemperature is high, for example 140 F. or above. There has, however,been a problem in achieving the combustion temperature for thecarbonaceous material when the initial temperature in the formation islow, for example 140 F. or below. This has been especially true in theformations which have low initial temperatures and contain water. Whenthe. initial temperature is low, the autoignitible fluids such aslinseed and tung oil increase in temperature slowly when contacted withair or other oxygen-containing, combustion-supporting gas. This slowincrease toward the combustion temperature of the carbonaceous materialmay result in failure to reach that temperature. This is due to the factthat the heat from the reaction can be dissipated into the surroundingstratum if the temperature rise is slow.

I have discovered that the above problem of heat dissipation can beovercome by using as an autoignitible fluid a combination of tung oiland tall oil fatty acid. The temperature of the tung oil-tall oil fattyacid mixture will rise rapidly when air or other oxygen-containing,combustion-supporting gas is contacted with the mixture in the stratum.This fast rise in temperature eliminates the possibility that the heatmay be dissipated in the stratum before the combustion temperature ofthe carbonaceous material is reached.

Accordingly, it is the object of the present invention to provide animproved process for igniting oil in an oil stratum wherein the stratumcontains water and has a low initial temperature. A further object is toprovide l 3,490,530 Patented Jan. 20, 1970 an improved process forigniting oil in an oil stratum wherein the stratum contains water andhas a low initial temperature by utilizing a mixture of tung oil andtall oil fatty acid as an autoignitible fluid. Other objects, aspectsand advantages of the invention will be apparent from a study of thedisclosure and the appended claims of the invention.

A broad aspect of the invention comprises dispersing a mixture of tungoil and tall oil fatty acid in a stratum containing carbonaceousmaterial and water and thereafter injecting an O -containing oxidizinggas into the stratum and into contact with the mixture so as to increasethe temperature of the stratum and the in place carbonaceous materialrapidly to a point at or above the combustion point of the carbonaceousmaterial. The tung oil makes up beween 70 to weight percent of the totalmixture and the tall oil fatty acid between 10 to 30 weight percent ofthe total mixture.

A normal procedure for placing the mixture of tung oil and tall oilfatty acid into an oil stratum is as follows: the mixture of tung oiland tall oil fatty acid is physically mixed in tanks on the surface.After the fuel is mixed, a slug is sent down the oil well. It has beenfound that incorporation of an oxidation catalyst in minor concentrationin the mixture facilitates spontaneous ignition of the mixture and makesit feasible to ignite the mixture with ordinary air at atmosphericpressure. It is preferred to utilize the catalyst in liquid form so asto avoid plugging the stratum. A preferred catalyst is cobaltnaphthenate, which is readily soluble in the tung oiltall oil fatty acidmixture. Other catalysts include oil soluble salts and other compoundsof the metals listed as oxidation catalysts in Berkman et al.,Catalysis, Reinhold Publishing Corporation, 330 W. 42nd St., New York,N.Y., 1940, pages 797-809. Next a nonoxidizing gas such as nitrogen orexhaust gas (nitrogen and C 2) is pumped into the well to disperse themixture in the stratum. The mixture will generally be dispersed out fora distance between about 1 and 10 feet from the well hole in thesurrounding stratum.

After the mixture is dispersed into the stratum then an oxidizing gassuch as air or other Op-containing, combustion-supporting gases isinjected into contact with the mixture. There will be a rapid increasein the temperature of the mixture when contacted with the air or otheroxygen-containing, combustion-supporting gases. This is true even whenthe initial temperature in the stratum is below F. (such as 80 F.).Also, there will be autoignition of the carbonaceous material even whenthere is water present in the stratum in percentages up to about 3weight percent water with particularly good results in stratumcontaining up to about 2.5 weight percent water. The temperature willcontinue to rise in the stratum until the combustion temperature of thecarbonaceous material in the stratum is reached. After the combustiontemperature of the carbonaceous material is reached, injection of theoxidizing gas is continued to ignite and burn the carbonaceous materialin place in the stratum.

Tests were run to demonstrate the facility with which the mixture oftung oil and tall oil fatty acid reached the combustion temperature foroil. In all the tests the initial temperature was 80 F. and the timerequired to reach 250 F. was measured. The temperature of 250 F. wasused because it was known that all autoignition fuels which reached 250F. will rapidly move on up to the combustion point of oil at about thesame rate. In other words, once the autoignition fuels reached 250 F.,then they all went from 250 F. to the combustion point of oil inapproximately the same amount of time. Also, since the temperature ofcombustion for oil is differentfor different oils and formations, theuse of 250 F. made the data easier to compare.

The procedure used for the first six tests was as follows: Theautoignition fuel was mixed with a 30-40 mesh silica sand Wetted with2.5 weight percent water. This mixture of fuel, water and sand waspacked into a nearadiabatic (heated wall) glass cylinder which was inturn installed in a steel pressure jacket. Air at a pressure of 900p.s.i. was put through the pack at controlled rates which started out at50 s.c.f. hour/ square foot and 80 F. The autoignitible fuels contained0.2 weight percent cobalt as cobalt naphthenate as oxidation catalyst.The procedure used for the last five tests was the same as for the firstsix tests except that no water was added to the sand in the last fivetests. All other conditions were the same. The initial temperature forall tests, as stated above, was 80 F. The followmg results weretabulated:

Water Time to in Sand Reach (Weight 250 F. Run Autoignition Fuelpercent) (Minutes) 1 100 Tun Oil 2.5 115 2 t 2. 100 3 90% Tung Oil, TallOil Fatty ci 2. 5 75 4 70% Tung Oil, 30% Tall Oil Fatty Acid 2. 5 70 5d0 2. 5 65 6 100% Tall Oil Fatty Acid--. 2. 5 7 100% Tung Oil 0 73 8 70%Tung Oil, 30% Tall O11 Fatty 1 Did not reach 250 F.

As shown by the above results, with the tung oil and tall oil fatty acidmixture there was a substantial decrease in the amount of time that wasrequired to reach the 250 F. point. This decrease in the time at which250 F. was reached assures that a system will reach the combustiontemperature of the oil and that the heat will not be dissipated fasterthan the temperature can rise. It is also shown that the oil can beignited from low initial temperatures even in the presence of water.This will eliminate the requirement that the water be evacuated from thestratum before the in place burning takes place.

We claim:

1. A process for injecting and burning carbonaceous material in an oilstratum, said stratum containing amounts of water up to 3 percent byweight, which comprises the steps of:

(1) injecting into said stratum a mixture comprising tung oil and talloil fatty acid where in said mixture said tung oil is from about topercent by weight of the total mixture and said tall oil fatty acid isfrom about 10 to 30 percent by weight of the total mixture; and

(2) subsequent to step (1), injecting an oxidant providing suflicient 0concentration to cause autoignition of said mixture into said stratuminto contact with said mixture.

2. A process in accordance with claim 1 comprising, in addition, a stepsubsequent to step 1) but prior to step (2) of injecting a nonoxidizingfluid into said stratum to force said mixture into said stratum.

3. A process in accordance with claim 1 comprising, in addition, a stepsubsequent to step (2) of continuing injection of said oxidant at a rateto ignite and burn the in place carbonaceous material.

4. A process in accordance with claim 1 wherein an oxidation catalyst isadded to said mixture in step (1).

5. A process in accordance with claim 4 wherein said oxidation catalystis cobalt naphthenate.

6. A process in accordance With claim 1 wherein said stratum containsamounts of water up to 2.5 percent by weight.

7. A process in accordance with claim 1 wherein the initial temperatureof said stratum and said mixture is less than F.

8. A process in accordance with claim 7 wherein the initial temperatureof said stratum and said mixture is about 80 F.

References Cited UNITED STATES PATENTS 2,863,510 12/1958 Tadema et a1.166260 3,026,937 3/1962 Simm 16626O 3,180,412 4/1965 Bednarski 166-2603,205,944 9/1965 Walton 166-26l 3,209,822 10/1965 Marberry 166'2563,221,809 12/1965 Walton 166263 3,285,336 11/1966 Gardner 1662613,314,476 4/1967 Staples et a1 166260 3,363,687 1/1968 Dean 16626O X3,379,254 4/1968 Holmes 166260 STEPHEN J. NOVOSAD, Primary Examiner U.S.Cl. X.R. 166-261

